HomeMy WebLinkAboutCT 83-19; CALAVERA HILLS VILLAGE T; SUMMARY OF GEOTECHNICAL INVESTIGATION E-1, E-2, H, K, L-2,L-3,Q,R,S,T,UAND W-X; 1984-08-06I
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SUMMARY OF GEOTECHNICAL INVESTIGATION
LAKE CALAVERA HILLS VILLAGES
E-1, E-2, H, K, L-2, L-3,
Q, R, S, T, U, AND W-X
CARLSBAD, CALIFORNIA
PREPARED FOR:
Ca1avera H111s Company
110 West "C" Street, Suite 1220
San Diego, California 92101
PREPARED BY:
Southern California Soil & Testing, Inc.
Post Office Box 20627
6280 Riverdale Street
San Diego~ California 92120
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SOUTHERN CALIFORNIA SOIL AND TESTING, INC.
62BO RIVERDALE ST. SAN DIEGO, CALIF'. 92120 • TELE 2BO-4321 • P.O. BOX 20627 SAN DIEGO, CALIF'. 92120
6 7 BEN T E R P R I S EST. ESC 0 N 0 I 0 0, CAL I F. 9 2 0 2 5 • TEL E 7 4 6 - 4 5 4 4 '
August 6, 1984
Calavera Hills Company
110 West "C" Street, Suite 1220
San Diego, California 92101
SCS&T 14112
Report No. 6
SUBJECT: Surrunary of Geotechnical Investigation for Lake Calavera Hills,
Villages E-1, E-2, H, K, L-2, L-3, Q, R, S, T, U, and W-X,
Carlsbad, California.
Gentlemen:
In accordance with your request we have prepared a summary of the findings
and conclusions of our geotechnical investigations for the subject pro-
ject. The purpose of this summary was to provide an overa 11 view .of the
geotechnical characteristics of the site and their influence on the devel-
opment of the property.
If you have any questions regarding this report, or if we may be of fur-
ther service, please do not hesitate to contact our office.
TESTING, INC.
37 Curtls R. Burdett, :C.E.G. #1090
Charles H. Christian, R.C.E. #22330
CHC:CRB:DBA:mw
cc: (6) Submitted
(1) SCS&T, Escondido
SOUTHERN CALIFORNIA SOIL AND TEE!TING, INC.
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TABLE OF CONTENTS
PAGE
Introduction and Project Description ••••••••••••••••••••••••••••••••••••• 1
Findings ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 3
General Site Description •••••••••••••••••••••• ~ •••••••••• j ••••••••••• 3
General Geology and Subsurface Conditions •••••••••••••••••••••••••••• 3
Geologic Setting and "Soil Description ••••••••••••••••••••••••••• 3
Basement Complex-Jurassic Metavolcanics and
Cretaceous Granitics (Jmv/Kgr) ••••••••••••••••••••••••••••• 4
Lusardi Formation (Kl) •••••••••••••••••••••••••••••••••••••••• 5
Tertiary Paleosol (Tp) •••••••••••••••••••••••••••••••••••• ~ ••• 6
Santiago Formation (Es) •••••••••••••••••••••••••••••••••• ~ •••• 6
Tertiary Volcanic Rock (Tv) ••••••••••••••••••••••••••••••••••• 6
Quaternary Sandstone (Qu) •••••••••••••••••••••••••• ~ •••••••• ~.7
Older Quaternary Alluvium (Qoal) ••••••••••••••••.••••.•••••••••• 7
Younger Quaternary Alluvium (Qyal) •••••••••••••••••••••••••••• 8
Artificial Fill (Qaf) •••••••••••• ~ •••••••••••••••••••••••••••• 8
Specific Village Geologic Condtions •••••••••••••••••••••••••••••••••• 9
General Rippability Characteristics ••••••••••••••••••••••••••••••••• 10
General •••••••••••••••••••••••••••••••••••••••••••••••••••••••• 10
Rippability Characteristics of Granodioritic Rock ••••••••••••••••••• 10
Rippable Condition ••••••••••••••••••••••••••••••••••••••••••••• 10
Marginally Rippable Condition •••••••••••••••••••••••••••••••••• 10
Nonrippable Condition •••••••••••••••••••• ~ ••••••••••••••••••••• 11
Rippability Characteristics of Metavolcanics and Associated
Hypabyssal Rocks and Tonalitic Rocks •••••••••••••••••••••••••••••• 11
Rippable Condition ••••••••••••••••• ~ ••• ~ ••••••••••••••••••••••• 11
Marginally Rippable Condition •••••••••••••••••••••••••••••••••• 12
Nonrippable Condition •••• ~ •••••••••••••••••••••••••••••••••••• ~12
Village Specific Rippability Characteristics •••••••••••••••••••••••• 12
Village E-l •••••••••••••••••••••••••••••••••••••••••••••••••••• 12
Village E-2 ••••••••••••••••••••••••••••••••••••••••••• -••••••••• 12
Village H •••••••••••••••••••••••••••••••••••••••••••••••••••••• 13
Village K •••••••••••••••••••••••••••••••••••••••••••••••••••••• 13
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TABLE OF CONTENTS (continued)
PAGE
Village L-2 •••••••••••••••••••••••••••••••••••••••••••••••••••• 13
Villages L-3 and Q ••••••••••••••••••••••••••••••••••••••••••••• 13
Village R •••••••••••••••••••••••••••••••••••••••••••••••••••••• 14
Village S •••••••••••••••••••••••••••••••••••••••••••••••••••••• 14
Village T •••••••••••••••••••••••••••••••••••••••••••••••••••••• 14
Village T South •••••••••••••••••••••••••••••••••••••••••••••• 14
Village T North ••••••••••••••••••••••••••••••••••••• ~ •••••••• 14
Village U •••••••••••••••••••••••••••••••••••••••••••••••••••••• 15
Village W-X •••••••••••••••••••••••••••••••••••••••••••••••••••• 15
Tectonic Setting and Geologic Hazards ••••••••••••••••••••••••••••••• 15
General Conclusions ••••••••••••••••••••••••••••••••••••••••••••••••••••• 17
Preliminary Recommendations ••••••••••••••••••••••••••• , ••••••••••••• 17
Site Preparation ••••••••••••••••••••••••••••••••••••••••••••••• 17
Subdrains •••••••••••••••••••••••••••••••••••••••••••••••••••••• 18
Rock Disposal ••••••••••••••••••••••••••••••••••••• ,.j.~ •••••••• 18
Select Grading ••••••••••••••••••••••••••••• ~ •••••••••• ~ •••••••• 18
Undercutti ng •••••••••••••••••••••••••• ~ ••••••••••• " ••••• ~ •••••••• 19
Slope Stability ••••••••••••••••••••••••••••••••••••••••••••••• " ••••• ,.,,19
General ••••••••••••••••••••••••••••••••••••••••• ~ •••••••••• ~ ••• 19
Villages H and W-X ••••••••••••••••••••••••••••••••••• ~ ••••••••• 20
Foundations ••••••••••••••••••••••••••••••••••••••••• ~ ••••••••••••• ~.20
General •••••••••••••••••••••••••••••••••••••••••••••••••••••••• 20
Reinforcing ••••••••••••••••••••••••••••••••• ~ •••••••••••••••••• 20
Concrete Slabs-on-Grade •••••••••••••••••••••••••••••••••••••••• 20
L imi tati ons •••••••••••••••••••••••••••••••••••••••••••••• " •••••• _ ••••••••• 21
Review, Observation and Testing •••••••••••••••••••••••• ~ ••• ~ •••••••• 21
Uniformity of Conditions •••••••••••••••••••••••••••••••••••••••••••• 21
Change in Scope ••••••••••••••••••••••••••••••••••••••• , ••••.••••••••• 22
Time Limitations •••••••••••••••••••••••••••••••••••••••••••••••••••• 22
Professional Standard •••••••••••••••••••••••••••••••••••• ~ •••••••••• 22
Client's Responsibility ••••••••••••••••••••••••••••••••••••••••••••• 23
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ATTACHMENTS
FIGURE
PAGE
Figure 1, Site Vicinity Map •••••••••••••••••••••••••••••••••••••••••••••• 2
TABLES
Table I, Generalized Engineering Characteristics of Geologic UnitS •••••• ~8
Table II, Specific Village Geologic Conditions ••••••••••••••••••••••• ~9-10
PLATE
Plate 1 Plot Plan
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SOUTHERN CALIFORNIA SOIL AND TESTING, INC.
62BO RIVERDALE ST. SAN DIEGO, CALIF. 92120 • TELE 2BO·4321 • P.O. BOX 20627 SAN DIEGO, CALIF. 92120
6 7 BEN T E R P R I S EST. ESC 0 N 0 I DC, CAL I F". 9 2 0 2 5 • TEL E 7 4 6 - 4 5 4 4
SUMMARY OF GEOTECHNICAL INVESTIGATION
LAKE CALAVERA HILLS
VILLAGES E-l, E-2, H, K, L-2, L-3, g, R, S, T, U, AND W-X
CARLSBAD, CALIFORNIA
INTRODUCTION AND PROJECT DESCRIPTION
This report presents a surrunary of the results of our geotechnical investi-
gation for the Lake Calavera Hills Subdivision Villages E-L, E-2, H, K,
L-2, L-3, g, R, S, T, U, and W located in the City of Carlsbad, Calif-
ornia. The site location is shown on the vicinity map provided as Figure
1.
The purpose of this summary is to provide an overall picture of the geo-
technical characteristics of the site and their effect on the potential
site development. Specifically this report includes the following items:
1) General Site Description.
2) General Geologic and Subsurface Conditions
3) Specific Village Geologic Conditions
4) General Rippability Characteristics
5) Specific Village Rippability Characteristics.
6) Tectonic Setting and Geologic Hazards
7) General Conclusions
8) General and Specific Village Recommendations
SOUTHERN CALIFORNIA SOIL AND TESTING, INC.
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SOUTHERN CALIFORNIA
SOIL & TESTING. INC.
IIRIID RIVERDALE IITREET
IIAN Dlil!l:JD, CALIFDRNIA IiIR1RD
BY
TE
Calaveras Hills
Carlsbad, California
DATE SMS 8':'6-84 1~ ____________________________________ ~ _______ 1_4_l_l_2 ______ ~_-_~_i_g_U_re_.·L_·N_o_._1 __ ~ __ ~
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SCS&T 14112 August 6, 1984 Page 3
To assist in the preparation of this report, we were provided with an
undated topographic map prepared by Charles W. Christensen and Associates.
The site configuration, approximate topography and geologic boundaries are
shown on Plate Number 1 of this report.
FINDINGS
GENERAL SITE DESCRIPTION
The subject site consists of twelve separate villages in the Lake Cal avera
Hills Subdivision in Carlsbad, California. Eleven of the villages are
contiguous and comprise the eastern portion of the Lake Calavera Hills
Subdivision; the remaining vil1age is separated from the others and con-
stitutes the extreme western portion of the subdivision. The morphology
of the site is characterized by bold, rugged hills with well-defined
drainage channels. Elevations range from approximately 100 feet (MSLD) on
the southern portion of the site to approximately 450 feet on the north-
central portion. r~ost of the site is in an undeveloped condition. A
large water tank is present on the high hi 11 in the n.orth-central portion
of the site (Village L-3) and a set of northeast trending power lines is
present on the eastern portion of the site (Villages R, T, U and W-X).
Portions of the site have previously been used for agricultural puposes
but the former fields are now fallow. Vegetation consists of a moderate
to heavy growth of native grasses, shrubs, and chaparral.
GENERAL GEOLOGY AND SUBSURFACE CONDITIONS
GEOLOGIC. SETIING AND SOIL DESCRIPTION: The subject site is underl ainby
materials of both igneous and sedimentary origin. Approximately 70% of
the site is underlain by the basement complex rocks consisting of Jurassic
metavolcani~ rocks and Cretaceous granitic rocks. Approximately 20% of
the site is underlain by the sandstones, siltstones, and claystones of the
SOUTHERN CALIFORNIA SOIL ANO TESTING. INC •.
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SCS&T 14112 August 6, 1984 Page 4
Eocene Santiago Formation. The remaining 10% of the site is underlain by
a variety of materials consisting of Cretaceous sediments, Tertiary pale-
osol, Tertiary volcanic rock, Pleistocene sandstone, Pleistocene alluvium,
H910cene alluvium, and man-made fill. A brief description of the mate-
rials encountered, in general decreasing order of age, is presented below.
It should be noted that the term IIrock ll as used in this report applies in
the geologic sense in that all native materials of igneous origin or
sediments that are sufficiently consolidated or coherent can be classified
as IIrock li • This term does not necessarily indicate that the materials are
not excavatable by conventional earth-moving equipment.
1) Basement Complex -Jurassic Metavolcanics and Cretaceous Gran-
itics (Jmv/Kgr): The oldest rocks exposed at the site are the
Jurassic metavolcanic and associated hypabyssal rocks. Both of
these rocks weather to dark, smooth hills or jagged, angular
outcrops with a clayey, rocky topsoil. The metavolcanic and
hypabyssal rocks are generally rippable with conventional earth-
moving equipment to depths of a few feet.
The other rocks in the basement comp 1 ex are the granitic rocks
which have intruded the older rocks and are, to a large degree,
mixed with them. The granitic rocks at the project site appear
-to be both tonalitic and granodioritic in composition. The
tonal itic rocks appear to be predominant in the southern' and
west-central portions of the site and the granodioritic rocks
appear to be restricted largely to the northern and northeastern
portions of the site. The weathering and rippabil ity character-
istics of the tonalitic rock,s appear to be somewhat similar to
those of the metavolcanic/hypabyssal rocks. The granodioritic
rocks on the other hand may be ri ppab 1 e to greater depths than
the metavolcanic rocks. In contrast to the weathering character-
istics of the metavolcanic/hypabyssal rock and the tonalitic
SOUTHERN CALIF'ORNIA SOIL AND TESTING. INC.
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SCS&T 14112 August 6, 1984 Page 5
rocks, the granodioritic rocks commonly weather to rounded out-
crops or boulders in a matrix of grus ("decomposed granite").
The granodioritic rocks are variable in their excavation charac-
teristics but commonly contain areas which are rippable to depths
of several feet to several tens of feet yet include' localized
areas of boulders or unweathered rock which are not rippable with
conventional heavy equipment~
The areas underl ai n by the respecti ve rock types in the basement
complex are differentiated on the accompanying geologic map. It
shou 1 d be noted that the different rock types are mi xed and the
areas on the map only indicate which rock type is dominant.
Where the symbol for the metavolcanic rock is listed first (ie:
Jmv/Kgr), the area is characterized largely by metavolcanic and
hypabyssa 1 rocks with 1 esser amounts of graniti c rock. Conver-
sely, where the symbol for the granitic rock is 1 isted first (ie:
Kgr/Jmv), the area appears to be underlain predominantly by
granitic rock with lesser amounts of metavolcanic and hypabyssal
rocks.
2) Lusardi Formation (Kl): The Lusardi Formation is a conglomerate
that rests nonconformably on the basement complex. This forma-.
tion conslsts largely of granitic and metavolcanic boulders in a
matrix of coarse grained sandstone and siltstone. The conglomer-
ate is usually poorly sorted and the clasts are commonly angular
to subrounded. The only area of Lusardi Formation on the subJect
site proper which is large enough to map as part of thisinvesti-
gation is 'on the extreme eastern portion of the site. Other
areas of Lusardi Formation may be encountered at other portions
of the, site in subsequent, more-detailed investigations.
SOUTHERN, CALIF"ORNIA SOIL AND TESTING. INC.
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SCS&T 14112 August 6, 1984 Page 6
3) Tertiary Paleosol (Tp): A zone of ancient p'a1eosolis present on
the basement complex and the Lusardi Formation in a few scattered
areas at the project site. This paleosol is th~ result of the
torrid climate and relatively stable geologic conditions that
were present in the San Diego area during the ~ar1y Cencrtoic era.
The resulting ancient soil (paleosol) is lateritic and consists
predominantly of low expansive clays. A thin residual cap of
ironstone concretious and siliceous pebbles is preseni on much of
the pa 1 eoso 1 • The thi ckness of' the pa 1 eos.o 1 was not determi.ried
but probably varies from a few feet to a few tens of feet. Only
a few areas of paleosol were sufficiently large to map as part of
this investigation. It should be noted that other, smaller areas
are present at scattered locations throughout the site.
4) Santiago Formation (Es): The sediments at the project site are
represented by the sandstones, si 1 tstones, and c1 aystones of the
Santiago Formation. The Santiago Formation in the western por-
tion of the site appears to be characterized largely by the
grayi sh white sandstones and si 1 tstones and dark greeni sh brown
claystone. Within the northern portion of -the site, the sedi-
ments cons; sts pri marily of sandstones. The Santiago Formati on
on the southern portion of the site appears to be predominantly
claystone with lesser amounts of sandstone and siltstone. A
well-developed, clayey topsoil is present on most of the Santiago
Formation. The claystones encountered withi~ this formation have
been associated to slope stability problems and may require
special grading consideration if deep and/or steep cut slopes are
proposed in the Santiago Formation deposits.
5) Tertiary Volcanic Rock (Tv): Cerro de la Calavera ;s part of a
volcanic neck that has intruded the older rocks in the Carlsbad
area. The volcanic rock is usually brown to brownish gray and
SOU THE R N CAL. I FOR N I A 5 0 I L. A NOT E 5 'T I ·N G·. I N ·C.
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SCS&T 14112 August 6, 1984 Page 7
appears to include both dacite and andesite. The weathering
characteristics and excavation characteristics ,of the Tertiary
volcanic rock are similar to those of the Jurassic metavolcgnic
rocks. The only area of Tertiary volcanic rock of sufficient
dimension to map for this project was found on the extreme east-
ern portion of the site, just west of Cerro de la Calavera. It
is possible that future grading operations or more detailed
geologic mapping may reveal more of the Tertiary volcanic rock on
site.
6) Quaternary Sandstone (Qu):
grayish brown to yellowish
stone was encountered at a
the site. This material
A small area of unconsolidated,
brown, fine to medium grained sand-
port i on of the northern boundary of
unconformably overlies the Santiago
Format i on and may poss i b 1 y be rewor ked Santo; a go Format; on mate-
rial. It is difficult to distinguish the Ql!aternary sandstone
from the Santiago Formation on the basis of their surficial
characteristics., This unit was observed in other areas in the
g'eneral vicinity and may possibly be encountered at other local-
ities on the project site during grading operations.
7) Older Quaternary Alluvium (Qoal): Older a 11 uvial deposits con-
sisting of grayish brown to yellowish brown and greenish brown,
medium dense, silty sands, clayey sands, ~nd sandy silts were
encountered at various locations at the project site. These
deposits range in thickness from only a few feet to in excess of
ten feet. Areas of sufficient lateral extent to map were encoun-
tered on the southeastern corner of the site and in the east-
central portion of the site. Smaller, un-mapped areas were
encountered at other scattered 1 ocat; ons. These deposits should
not require any special grading process and should be suitable in
their natural condition to support fills and/or structures.
SOUTHERN CALIF'ORNIA SOIL ANO TESTING. INC.
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SCS&T 14112 August 6, 1984 Page 8
8)
9)
Younger Quaternary All UYi urn (Qya 1 ): Younger alluvi-al deposits
consisting of loose to medium dense deposits of clay, silt, san~,
and gravel are present in the modern stream channels. These
depos its range in thi ckness from 1 ess than a foot "to over ten
feet. Due to their ubiguitous occurrence, the younger alluvial
deposits are not delineated on the geologic map except in the
larger channels. These deposits will require remedial grading.
Artificial Fill (Qat): Severa 1 small areas of man-made fi 11
which have been obtained from on-site or nearby sources were
observed. These area are genera 11 y limited to small earthen
dams, minor roads associated with previous agricultural opera-
tions, or the remnants of a previous rock-crushing operation on
the eastern boundary.
Table No.1 presents some of the pertinent engineering characteristics of
the materials encountered at the site.
TABLE I
GENERALIZED ENGINEERlHG CHARACTERISTICS OF GEOLOGIC UNITS
Unit .. ,. AIIount of Slope Exp.nshe
.nd S>'lIIOol Rtpp!bt IitI Oyersize H.teri~1 SUDt 1 tty/Erosion CDllPress i 01 I tty Potent hi
TOPS011s R1pp.ble Nonl1,..1 "Oder.t •• , to l'IootrUt to H191'1. Low to H19h
H191'1.1)' ErOdible
Younger Rlpp.ble 1'1011,",1 Moderately to HOderite to H19" HOGer.te
A,lluytUIII-Qy.1 H19hl1 Erodtole to high
Older Rtpp.ole Nann".' HodtrUely HOGerate to H t 91'1. Low to
Alluyil".Qcwl £rOdlol. hlgn
Unn.Md RtpP'b)e HCllltn.l Hignly Erodible Low to MOdernt Low to
QuAternary HOderltt
S.ndstone .. Qu
Tert1iry Hlrgl".11,)' HOCIer.tt Gener.lIy GOOd HOIIItn.1 HOMtna'
Volc.nic R1pp.ble to to HIgh
RoCk-tv Nonr1;1pible
S.nti.go Rlpplbl. NOII1n.t Gtnerally GOOd Low Low to
Fo .... t1on .. £s "OC1erlte
(S.ndnone ,
Siltstone)
5.nt1l.90 Ripplele NOIItn.t Generilly Poor Low "OI3true to
Fonut1on .. £s HIgh
(Huo .. on.)
T'!rt:ury R1pplble to Low Fitr Low Low
PilROsol-Tp H'1"91n.lly
RiPPlb1e
LuSird1 RiPPlbl, Low to Modernlly Low Low
FOnHt1on .. Kl Koderne Erodible
GrlnitiC ROCks .. GIM'erll1y Low to GoOd NDlW1nlt NOllnn.l
Kgr R1pp.ble to KOClerUt
(Gr.nodtor'ltt) 't lS Feet
GrlnitiC Rocks-Kirginll1, KOderate GOOd HOIItnil ItoOlnll
Kgr {Toni lito) RiPPlb}' to to High
HonriPPlbl.t
Keuvol""lC , Mlr91nl11, MOCtrlte GOOd HOftItn.l Nomin.l
Hyp.bYSSil R1PPlblt to t.o High
Rock.s-JIIV HonriPPlale
SOUTHERN CALIFORNIA SOIL ANO TESTING. INC.
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SPECIFIC VILLAGE GEOLOGIC CONDITIONS
The following Table No. II 1 ists the main geologic units encountered at
each proposed village and their approximate extent of surface coverage.
Vi 11 age
E1
E2
H
K
L-2
L-3 & Q .
R
S
T South
T North
TABLE II
Geologic Unit
Kgr /Jmv
Jmv /Kgr
Jmv /Kgr
Es
Qyal
Jmv /Kgr
Kgr/Jmv
Jmv/Kgr
Kgr /Jmv
Kgr/Jmv
Jmv/Kgr
Qyal
Es
Kgr/Jmv
Jmv /Kgr
Tp
Qyal
Jmv /Kgr
Kgr Nmv
Qoal
Tp
Es
Kgr /Jmv
Qu
Qyal
Qoal
Tp
Percent of Surface Coverage
60%
40%
100%
95%
5%
55%
45%
60%
40%
54%
44%
2%
100%
80%
15%
3%
2%
68%
15%
15%
8%
75%
10%
10%
3%
1%
1%
SOU THE R N c: A L t F' 0 R N I A 5 0 I LAN· 0 TEST I N G. I.N C:.
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SCS&T 14112 August 6, 1984 Page 10
TABLE II (continued)
Village Geologic Unit Percent of Surfac,e Coverage
u
w-x
Jmv/Kgr
Kgr/Jmv
Kl
Qyal
others
Jmv/Kgr
Kgr /Jmv
Qoal
Es
Tp
GENERAL RIPPABILITY CHARACTERISTICS
80%
10%
5%
3%
2%
70%
15%
8%
6%
1%
GENERAL: The rock encountered at the site may be classified as rippable,
moderate ly ri ppab 1 e and nonri ppab 1 e. Depend i ng upon the rock type, the
material generated from the excavations and the effort required to achieve
the proposed cuts will vary. Our seismic survey indicated that areas
underlain by granitic rock have rippable material to depths ranging from
30t feet to 19t feet, with nonrippable material below this depth. In
areas underlain by metavolcanic and associated hypabyssal rock, rippable
material appears shallower and extend to depths ranging from 4t feet to
2it feet. In addition, a variable zone of marginally rippable rock usu-
ally exists between the rippable and nonrippable rock. This zone can
range in depth fram 3t feet to 2it feet. Presented herein is a sumnary of
the rippability characteristics of the different rock types encountered at
the site.
RIPPABILITY CHARACTERISTIC OF GRANODIORITIC ROCK
Rippable Condition: This velocity range indicates rippable materials
which may consist of decomposed granitics possessing random hardrock·
floaters. These materlals will break down into slightly silty, well graded
SOU THE R N CAL 1 FOR N 1 A S a I'L A NOT EST 1 N ,C;. INC.
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SCS&T 14112 August 6, 1984 Page 11
sand, whereas the floaters will require disposal in an area of nonstruc-
tural fill. Some areas containing hardrock floaters may present utility
trench problems. Further, large floaters exposed at or near finish grade
may present additional problems of removal and disposal.
Materials within the upper rippable range are rippable with difficulty by
backhoes and other light trenching equipment.
Marginally Rippable Condition: This range is rippable with effort by a
0-9 in only slightly weathered granitics. This velocity range may also
include numerous floaters with the possibility of extensive areas of
fractured granitics. Excavations may produce material that will partially
break down into a coarse, slightly silty to clean sand, but containing a
high percentage of + 1/4" material. Less fractured or weathered materials
may be found in this velocity range that would require brasting to facili-
tate removal.
Materials within this range are beyond the capability of backhoes and
lighter trenching equipment. Difficultiy of excavation would also be
realized by gradal Is and other heavy trenching equipment.
Nonrippable Condition: This velocity range includes nonrippable material
consisting primarily of fractured granitics at lower velocities with
increasing hardness of fractured granitics at higher velocities. in its
natural state, this material is not desirable for building pad subgrade.
Blasting will produce oversize material requiTing disposal i.n. areas of
nonstructural fill.
RIPPABIlITY CHARACTERISTICS OF METAVOlCANICS AND ASSOCIATED HYPABYSSAL
ROCKS AND TONALITIC ROCKS
Rippable Condition: This velocity range indicates rippable materials
which may vary from decomposed rock at lower velocities to only slightly
SOUTHERN CALIFORNIA SOIL AND TE5TINI? ·INC.
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SCS&T 14112 August 6, 1984 Page 12
decomposed, fractu red rock at the hi gher ve 1 oc it i es. Although ri ppabl e;
materials may be produced by excavation that will need mixing with fines
prior to their placement in structural fills. Experience has shown that
material within the upper range of the rippable condition most often
consists of severely to moderately fractured rock with little or no fines
and sizeable quantities of + 1/411 material. Within this upper range,
rippability will be difficult for backhoes and light trenching eqUipment •
Marginally Rippable Condition: Excavations in this velocity range would
be extremely time consuming and would produce fractured rock with 1 ittle
or no fines. The higher velocities could require blasting. Trenching
equipment would not function.
Nonrippable Condition: This velocity range may include moderately to
slightly fractured rock which would require blasting for removal. Mate-
rial produced would consist of a high percentage of oversize and angular
rock.
VILLAGE SPECIFIC RIPPABILITY CHARACTERISTICS
Village E-1: This village is underlain by both metavolcanic and grani-
tic (tonalite) rock. Metavolcanic rock is exposed on the ~outhwestern
portion of the village. The metavolcanic rock may be rippable to a depth
of 1st feet. It also presents a zone of marginally rippable rock over-
lying the nonrippable material ranging in depth from 3t feet to lIt feet.
It is anticipated that granitic rock will be rippable to a depth of approx-
imately 10 to 15 feet and that approximately 50% of this material will
consist of soil and 50% will consist of rock.
Village E-2: Village E-2 is underlain predominantly by metavolcanic rock.
This material may be rippable to a depth of 1St feet. It also presents a
variable zone of marginally rippable rock overlying the nonrippable rock
ranging in depth from 3t feet to 16t feet.
SOU THE R N CAL I F" 0 R N I A SOl LAN 0 TEST I N G·. INC •
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SCS&T 14112 August 6, 1984 Page 13
Vi 11 age H: Vill age His under I ai n by sandstones, si I tstones and c1 ay-
stones of the Santiago Formation which are rippable with conventional
grading equipment.
Village K: This village is almost evenly divided between granitic and
metavolcanic rock with the majority of the granitic rock underlying its
central section. It is anticipated that granitic rock (tonalite) will be
rippable to a depth of approximately 16 to 8 feet. This material wi 11
consist of approximately 50% rock and 50% soil. The metavolcanic rock may
be rippable to a depth of 9t feet. It also presents a zone of marginally
rippab1e rock overlying the nonrippable material ranging in depth from 5t
feet to 9t feet.
Village L-2: Approximately two-thirds of Village L-2 are under1atn by
metavolcanic rock which is rippable to a depth of 6t feet. It also· usually
presents a zone of marginally rippable rock overlying nonrippab1e mate-
rial. Granitic rock (granodiorite) comprises the western portion of the
village. This material is rippable to depths of 21t feet. The rippable
granitic rock consists of decomposed granite (silty sands) with some
boulders.
Villages L-3 and Q: Villages L-3 .and Q are approxfmately equally divided
between metavolcanic and granitic rock. Most of the metavolcanic rock
appears to be concentrated at the southern and eastern portions of the
village. Granitic rock (granodiorite) underlies the western central and
northern sections of the village. It is anticipated that granUic rock
wi 11 be ri ppable to depths ranging from approximately 19 feet to 10 feet.
This rippable material consists of decomposed granite (silty sands) with
some bou1 ders. Random margi na lly ri ppabl e areas rangi ng in depth from 0
to 30 feet may also be anticipated. Metavolcanic rock may be rippable to.
depths rangi ng from 8t feet to llt feet. It also usually presents a zone
of marginally rippab1e rock overlying the nonrippable material.
SOUTHERN CAL.IF"ORNIA 5011-ANO TESTING. INC.·
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Village R: Village R is underlain by sandstones of the Santiago Formation
which are rippable with conventional grading equipment.
Village S: Village S is primarily underlain by granitic rock (granodio-
rite). It is anticipated that the granitic rock will be rippable to
depths of approximately 10 feet to several tens of feet. Rippable mate-
rials will consist in general of decomposed granite (silty sands) with
occasional boulders. Metavolcanic rock may be rippable to a depth of 4t
feet. A zone of marginally rippable rock usually overlies the nonrippable'
materi al.
Village T: This village is divided into two parts connected by a narrow
corridor.
Village T South: More than half of Village T South is underlain by
metavolcanic rock with the remainder of the village approximately
evenly divided between older alluvial deposits and granitit roc~ (gran-
odiorite). Some paleosols also exist in this village. The older
alluvium is rippable with conventional grading equipment. It is
anticipated that the granitic rock will be rippable to depths of
approximately 10 feet to several tens of feet. Rippable granitic Tock
will consist primarily of decomposed granite (silty sands) with some
boulders. Metavolcanic rock may be rippable to a depth of 4t feet.
It also usually presents a 'zone of marginally rippable rock overlying
the nonrippable material.
Village T North: This village is prim~ri1y underlain by sandstones
which are rippable with conventional grading equipment. These depos-
its are known to extend to at least 30 feet below existing grade and
probably extend to a depth of several tens of feet. Most of Vi llage T
North will provi de an excellent source of si lty sands for use el se-
where at the site. Some granitic rock (granodiorite) exists at the
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SCS&T 14112 August 6, 1984 Page 15
southern portion of the vi llage. It is anticipated that this material
will be rippable to depths of approximately 10 feet to several tens of
feet. The rippable granitic rock will consist of decomposed granite
(silty sands) with some boulders.
Village U: Most of Village U is underlain by m'etavolcanic rock, sprink-
led with small isolated zones of granitic rock (tonalite). It is antici-
pated that granitic rock will be rippable to a depth of approximately 10
to 15 feet and that the rippable material will be approximately evenly
divided between rock and soil. Metavolcanic rock may be rippable to a
depth of 4t feet. It also usually presents a zone of marginally rippable
rock overlying the nonrippable material.
Village W-X: Most of Village W-X is, underlain by metavolcanic rock,
sprinkled with small isolated zones of granitic rock (tonalite). It is
anticipated that granitiC rock will be rippable to a depth of aproximately
10 to 15 feet. However within the southern portion of the vi llage the
granitic rock will be rippable to a depth of approximately 19 feet to 16
feet. Approximately 50% of the rippable granitic rock will consist of
soil and other 50% will be rock. Moderately rippable granitic rock may be
anticipated between 16t feet to 19t. feet. Metavolcanic rock may be rip-
pable to a depth of 4t feet. It also usually presents a zone of marginally
rippable rock overlying the nonrippable material.
TECTONIC SETTING AND GEOLOGIC HAZARDS
A few small, apparently inactive faults have been mapped previously at the
site. No evidence of faulting was noted in our exploratory trenches for
this investigation but it is possible that future grading operations at
the site may reveal some of these faults. Due to their status of activity ,
and geometry, these small faults should be of only minor consequence to
the proj ect.
SOUTHERN CALIF'ORNIA 5011-ANO TESTING. INC.
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SCS&T 14112 August 6, 1984 Page 16
In addition, it should be recognized that much of Southern Cal ifornia is
characterized by major, active fault zones that could possibly affect the
subject site. The nearest of these is the Elsinore Fault Zone, located
approximately 20 miles to the northeast. It should also be noted that the
possible extension of the Rose Canyon Fault Zone is located approximately
8 miles west of the site. The Rose Canyon Fault Zone is currently classi-
fied as only potentially active, rather than active, according to the
criteri a of the Cal Horni a Di vi si on of Mi nes and Geology. Due to the
current classification of the Rose Canyon Fault Zone, it is our opinion
that it should not be used as the desi gn earthquake source for conven-
tional residential structures. In our opinion the potential for damage
due to groundshaking in the San Diego County area is considerable less
than other parts of California.
The project site is located in an area which is relatively free of signi-
ficant geologic hazards. The most 1 ikely geologic hazard to affect the
site is groundshaking as a result of movement along one of the major,
active fault zones mentioned previously. Based on a maximum probable
earthquake of 7.3 magnitude along the Elsinore Fault Zone, maximum ground
acceleration at the site could be as high as 0.25 g. Conventional resi-
dential structures, four stories or less in height, that are constructed
in accordance with the minimum standards of the Uniform Bui lding Code
should be able to withstand accelerations of this level without experienc-
ing structural distress.
Another potential geologic hazard which may affect the site is the possi-
bility of slope stability problems associated with either adverse jointing
conditions in the various rock units or low strength parameters of the
claystones in the Santiago Formation. Remedial measure may be required
depending upon· the proposed cut slope hei ghts and incl ination. In our
opinion, the potential for this geologic hazard is low.
SOUTHERN CALIFORNIA SOIL ANO TESTING. INC.
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'SCS&T 14112 August 6, 1984 Page 17
GENERAL CONCLUSIONS
No geotechnical conditions were encountered which would preclude the
development of the site. Since no special details are presently known
regarding the development of the individual villages, the following recom-
mendat ions are genera 1 and fu rther geotechni ca 1 work may. be requ i red once
the specific development plans are defined.
The main condition affecting site development is the presence' of granitic
and metavo 1 cani crock underlyi ng approximately three-fourths of the site.
Depending upon the proposed final grade, some of these materials may
require blasting. Grading plans should minimize the .depth of cuts to
reduce the potential for blasting.
Some areas qre under I a in pri marily by meta vo 1 cani c and associ ated hypabys-
sal rock. It is anticipated that the material ge.nerated from the cuts of
these materials may contain relatively low amounts of fine soils. Since
rock fills require a percentage of fine soil in excess of that anticipated
from the mining of the site, importing of fine material or exporting
excess rock may be necessary if large cuts are proposed in metavolcanic
rock.
PRELIMINARY RECOMMENDATIONS
SITE PREPARATION: Site preparation consists of the removal of all exist-
ing vegetation and deleterious matter and, the removal andrecompaction of
loose surficial deposits such as topsoils, fills and younger alluvium.
The extent of topsoils removal and recompaction will only be approXimately
one or two feet in areas underlain by rock or Santiago Formation deposits,
respectively. Existing fills and younger alluvium are present only in
minor, scattered areas of the site.
SOU THE R N CAL I FOR N I A 5 0 I LAN 0 T E. 5 TIN G. I Nt;:.
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SCS&T 14112 August 6, 1984 Page 18
SUBDRAINS: Subdrai ns wi 11 be requi red along the bottom of canyons to
receive more than ten feet of fill.
ROCK DISPOSAL: Depending upon the depth and location of the proposed
cuts, some amounts of shot-rock and bou 1 ders wi 11 be generated du ri ng
grading. This material will require special, handling such as mining with
fine soils and/or placement as rock fills.
SELECT GRADING: The presence of expansive soils within 2.5 feet from
finished grade will require special foundation consideration in the form
of increased footing depths and/or reinforcement. If this condition is
not acceptable, select grading may be performed. Select grading in cut
areas consists of the removal of any expansive soils within 2.5 feet from
finished grade and their replacement with compacted nonexpansive soils •.
In fill areas expansive soils are not placed within 2.5 feet from· finish
grade. In general, most of the expansive soils at the site consist of
loose topsoils to require removal and recompaction. Therefore, their
placement below the aforementioned plans will not require any additional
gradi ng cost. Expansi ve soil s withi n formati anal deposits may beencoun-
tered in Village W-X and in random areas of Village ~.
I n genera l, moderate 1 y to hi gh 1y expans i ve soil s were encountered in the
following areas:
a) Thin zones of nearsurface expansive soils (average thic;kness l.at
feet) capping areas underlain by metavolcanic and granitic rock.
b) Some minor alluvial deposits were found to be expansive, primarly
in Village W-X and some of the alluvium in Village T.
c) Random lenses of expansive claystones and siltstones within the
Santiago Formation deposits of Village H.
SOUTHERN CALIFORNIA SOIL ANO TESTING, INC.
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SCS&T 14112 August 6, 1984 Page 19
d) Mudstones of Santiago Formation in Village W-X.
e) Expansi ve topsoi 1 sand nearsurface zones of expansi ve weathered
material (average thickness 2.0 feet) were encountered. in areas
underlain by Santiago Formation Deposits.
f) Portions of the Quaternary sandstone in Village S were found to
be moderately expansive.
Additional select grading may be required in order to provide enough fines
for rock fills. A primary source of fines within the site are Village H
and the northeastern section of Village T Which are underlain by sedi-
ments. In addition cuts less than 1st feet deep in areas underlain by
granodiritic rock (Villages E-1, K, Q and S) should generate 'select mate-
ri a 1 •
UNDERCUTTING: In order to facilitate foundation excavations within cut
areas underl ain by hardrock, it is suggested that said areas be undercut
to a depth of 12 inches below the bottom of the footing and be replaced
with compacted nonexpansive soil. This procedure may also be advantageous
for the construction of utility trenches in building pad areas. Since the
total areas required should not be large, utility line "alleys" may be
created by concentrating the lines in narrow undercut zones.
SLOPE STABILITY
GENERAL: It is our opinion that fi 11 slopes constructed with material
derived from the rock or Santiago Formation deposits and with a 2:1 (hori-
zontal to vertical) inclination will be stable against deep-seated failure
to heights of at least 60 feet. Cut slopes in rock and Santiago Formation
deposits constructed at an incl ination of 2: 1 should al so be stable to
heights of at least 100 feet. Isolated cut slope areas may present out of
SOUTHERN CALIFORNIA SOIL ANO TESTING. INC.
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SCS&T 14112 August 6, 1984 Page 20
face jOi nts and fractures whi ch may requi re remedial procedures such as
rock bolting. However, in our opinion, the extent of this problem will be
at the most, minor.
VILLAGES HAND W-X: Relatively weak siltstone and claystone layers were
encountered in the Santiago Formation deposits underlying Village H.
Santiago Formation debris within Village W-X consist primarily of mud-
stones. Depending upon the height of proposed slopes and their inclina-
tions, slope stabilization measures such as buttressing may be required if
large, steep slopes are constructed.
FOUNDATIONS
GENERAL: Conventional spread footings founded at least 12 inches below
lowest adjacent finished grade and having a minimum width of 12 inches are
recorTlTlended for the support of si ngl e story structures. Thi s mini mum
depth should be increased to 18 and 24 inches for two and three to four
story structures respectively. The minimum width should also be increased
to 15 and 18 inches for two and three or four story buildings, respec-
tively.
REINFORCING: It is recorrunended that mini mum rei nforcement consi st ·of two
continuous No.4 reinforcing bars, one located near the top of the footing
and one near the bottom. Additional reinforcing may be necessary for
structures over sharp transition between cut and fill and where expansive
soils exist within 2.5 feet of finish grade.
CONCRETE SLABS-ON-GRADE: Concrete slabs-on-grade should have a minimum
thickness of four inches and be reinforced with a 6 I x6"-W1.4xW1.4 (6 I1x6"-
10/10) welded wire mesh throughout. Where moisture sensitive floor cover-
ings are planned, the slab should be underlain by a visqueen moisture
barrier. A two-inch thick layer of sand should be provided above the
visqueen to allow proper concrete curing.
SOUTHERN CALIF'ORNIA SOIL ANO TESTING. INC.
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SCS&T 14112 August 6, 1984 Page 21
LIMITATIONS
REVIEW, OBSERVATION AND TESTING
The recommendations presented in this report are contingent upon our
review of final plans and specifications. The soil engineer and engineer-
ing geologist should review and verify the compliance of the final gra'ding
plan with this report and with Chapter 70 of the Uniform Building Code.
-It is recommended that the soil and foundation engineer be retained to
provide continuous soil engineering services during the earthwork opera-
tions. This is to observe compliance with the design concepts, specifica-
tions or recommendations and to allow design changes in the event that
subsurface conditions differ from those anticipated prior to start of
construction.
UNIFORMITY OF CONDITIONS
The recommendations and opinions expressed in this report reflect our best
estimate of the project requirements based on an evaluation of the subsur-
face soil conditions encountered at the subsurface exploration locations
and the assumption that the soil conditions do not deviate a,ppreciably
from those encountered. It should be recogni zed that the performance of
the foundations and/or cut and fill slopes may be influenced by undis-
closed or unforeseen variations in the soil conditions that may occur in
the intermediate and unexplored areas. Any unusual conditions not covered
in this report that may be encountered during site development should be
brought to the attention of the soils engineer so that he may make modifi-
cations if necessary.
SOUTHERN CALIFORNIA SOIL AND TESTING. INC.
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SCS&T 14112 August 6, 1984 Page 22
CHANGE IN SCOPE
This office should be advised of any changes in the project scope or
proposed site grading so that it may be determined if the recomnendations
contained herein are appropriate. This should be verified in writing or
modified by a written addendum.
TIME LIMITATIONS
The findings of this report are val id as of this date. Changes in the
condition of a property can, however, occur with the passage of time,
whether they be due to natu ra 1 processes or the work of man on thi s or
adjacent properties. In addition, changes in the State-of-the-Art and/or
Government Codes may occur. Due to such changes, the findings of this
report may be invalidated wholly or in part by changes beyond our control.
Therefore, this report should not be relied upon after a period of two
years without a review by us verifying the suitability of the conclusions
and recommendations.
PROFESSIONAL STANDARD
In the performance of our professional services, we comply with that level
of care and skill ordinarily exercised by members of our profession cur-
rently practicing under similar conditions and in the same locality. The
client recognizes that subsurface conditions may vary from those encoun-
tered at the locations where our borings, surveys, and explorations are
made, and that our data, i nterpretati ons, and recomnendati ons are based
soley on the information obtained by us. We will be responsible for those
data, i nterpretati ons, and recommendati ons, but shall not be responsi bl e
for the interpretations by others of the information developed. Our
services consist of professional consultation and observation only, and no
warranty of any kind whatsoever, express or implied, is made or intended
SOUTHERN CALIFORNIA SOIL AND TESTING. INC.
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SCS&T 14112 August 6, 1984 Page 23
in connection with the work performed or to be performed by us, or by our
proposal for consulting or other services, or by our furnishing of oral or
written reports of findings.
CLIENT'S RESPONSIBILITY
It is the responsibility of Calavera Hills COqJany or thei-r representa-
tives to ensure that the information and reconvnendations contained herein
are brought to the attention of the engineer and architect for the project
and incorporated into the project's plans and specifications. It is
further their responsibility to take the necessary measures to ensure that
the contractor and his subcontractors carry out such recommendations
during construction.
SOU THE R N CAL I FOR N I A 5 0 I LAN 0 T EST I N G. I N, C •